1. Field of the Invention.
The invention concerns a bucket excavator whose working implement (e.g. a bucket) is pivotally connected to a bucket arm with an operating hinge and which has a drive consisting of a pair of cylinders on opposite sides of the operating hinge axis to rotate the implement about that axis.
Accordingly, the bucket excavator in accordance with the invention is a single-scoop excavator whose digging scoop is preferentially constructed as a bucket that can be exchanged for another bucket. The excavator in accordance with the invention can, moreover, be designed as a universal excavator in order, other than with different buckets, to also be equipped with other working equipment, e.g. a pile driver or a similar apparatus. Preferentially, however, the invention is realized as a precision excavator that displays a straight line guidance of its bucket in the scraping plane; therefore, the invention will be described in the following with the the aid of an excavator of this type.
2. Description of the Prior Art.
In the case of bucket excavators, the bucket arm most often sits at the tip of the split-up boom, whereby the parts are connected to one another over operating hinges with hinge axes that run transversely to the perpendicular plane of rotation of the boom, as well as being actuated by means of double-acting working cylinders, the drive for which is generally hydraulic. Here, the digging tool is connected on one side with an operatng hinge at the tip of the bucket arm and has its own operating cylinder that is connected, in the case of precision excavators, to the boom. The pivoting movement of a bucket serving as a digging took about the axis of the operating hinge located at the end of the bucket arm serves for filling and emptying the bucket and additionally functions for setting the angle of cut of the bucket blade and/or of the ripping teeth attached thereon.
The kinematics of a bucket excavator of the type just discussed requires that the plane of the bucket running transversely to the boom and/or the bucket blade run parallel to the ground level plane of the excavator, provided no correction capability is built in. Although it is basically possible to construct the caterpillar or wheel travel mechanism of the excavator to be pivotable relative to the top carriage, or to build in a correcting linkage in order to be able to adjust the cutting plane of the excavator independently of the ground level plane of the lower carriage, it is particularly advantageous to incorporate a correction linkage with the hinge axis lying in the perpendicular plane of rotation of the boom between the bucket and the bucket arm. The drive for the linkage is split-up between the two working cylinders that are disposed on either side of the hinge pin. This common arrangement of the working cylinders, also in the case of other operating hinges, enables dividing the pivoting forces between the two operating cylinders which, in this fashion, are given comparably smaller dimensions. It additionally has the advantage of a lesser bearing loading in the operating hinge. The invention relates in particular to the operating hinge that immediately adjoins the bucket and, therewith, preferentially on the correction linkage described, for the purpose of altering the scraping plane relative to the ground level plane of the lower carriage of the excavator, which is preferentially provided on the precision excavators.
Excavators performance can be optimized by incorporation of different digging scoops. In the case of loose, light earths, a large volume bucket can provide the best working results, while in rocky ground a smaller, but stronger, bucket will be required. Because of the good steering properties, precision excavators are particularly suited for making ditches (trenches). For this purpose, one advantageously makes use of a bucket whose profile corresponds to the ditch profile. If one makes use of the excavator for planing, particularly favorable then are wide and, most often, flat buckets. Even if an excavator of this type is not outfitted with other working equipment, simply because of the different buckets alone, the working equipment must be changed more frequently. Then, optimizing of the performance of the excavator depends on the timely replacement of the working equipment and, therewith, upon whether the replacement can be carried out rapidly, and without special expense for power, inasmuch as possible alone by the excavator operator.
If for this purpose one installs components of excavator mechanics, e.g. constructs the bolts of the operating hinge separately and capable of being actuated hydraulically for release and/or for gripping the hinge housing or casing, there then results an additional hydraulic drive that is difficult to adapt into the hydraulic supply and control of the excavator. Additionally, the operating hinge will be complicated and the replacement of the working implement will be difficult for the excavator operator. If, on the other hand, one makes provision for incorporating a mechanical coupling between the bucket and the operating hinge for replacement of the working implement, the parts of which one brings together or releases from one another by swinging the excavator boom, then a hydraulic coupling locking means must be integrated into the hydraulics of the excavator if the excavator operator is to undertake replacement of the working implement alone. This presents practically the same difficulties as an addditional hydraulic drive. The coupling mechanism additionally presumes that each working implement will be outfitted with a coupling half, which is relatively more expensive than separating the hinge bolt.
The invention is an improvement upon the precision excavator shown in German patent application DE-OS No. 28 51 942 and U.S. Pat. No. 4,277,899, because, in the case of that bucket excavator, the operating hinge adjoining the bucket represents a correction linkage within the idea explained above, which is actuated by two working cylinders. If the working implement is to be replaced, the operating hinge must be disassembled in order, after disconnecting the piston rods of the working cylinders from the bucket brackets, to release the bucket arm for replacement. Just as expensive is mounting the bucket or another working implement that is to be exchanged for the disassembled bucket.
The use of known mechanisms for simple replacement of the working implement of an excavator of this type already founders due to the fact that this changes the height of the operating hinge above the digging (ditching) tool so strongly that straight line guidance of the bucket is lost. In the case of the precision excavators, this straight line guidance is achieved by fine-adjustment of various linkage parallelograms, into which the parts of the boom and of the working cylinders articulated to a pivoting lever of the bucket are drawn. In general, in the case of a precision excavator, the above described remaining disadvantages of these known mechanisms would also take on particularly great importance.
The task underlying the invention is to enable replacement of the working implement on a bucket excavator and, in so doing, to construct the required mechanisms and their drives simply and such that they do not disturb the straight line steering of a precision excavator of the prior art and, in the case of other bucket excavators, to enable retaining the hydraulic drive without essential alteration of the hydraulic system with only negligibly changed attaching means for the working implement, whereby only few and inexpensive parts remain on the working implement that has been replaced.